1. sound cannot be heard on moon.why/ 2.velocity of sound is higher on hot summer day.why/ 3.sound needs a material medium to propagate.give reason. 4.rampant loudspeakers are curved.why?

(1) Sound needs a medium to travel. On earth we hear sound because sound has the medium air to travel from one point to another. On moon there is no atmosphere. So, sound cannot travel from one point to another. So, sound cannot be heard on the moon.

(2) Velocity of sound is higher on hot summer day since sound travels in mechanical waves. A mechanical wave is a disturbance that moves and transports energy from one place to another through a medium.And the medium can be any series of interconnected and interactive particles.Now as the energy of the molecules on a hot day is greater so molecules vibrate faster and results in quick disturbances and hence transfer energy with better rate.

(3) Why sound needs a material medium to propagate that can also be explained by the above point.